The usefulness of phenols in stabilizer compositions for synthetic resins was recognized early in the development of polymer stabilization by additives, as disclosed for example by F. Duggan in U.S. Pat. No 2,126,179 of Aug. 9, 1938, W. Leistner in U.S. Pat. No 2,564,646 of Aug. 14, 1951, and W. Fischer in U.S. Pat. No. 2,625,521 of Jan. 13, 1953, in the stabilization of polyvinyl chloride resin compositions. Over the years, phenolic stabilizers have been used in an expanding variety of synthetic resins and an enormous number of disclosures of new phenolic stabilizers has accumulated. Rather than attempt to list every one of these disclosures, A. DiBattista in U.S. Pat. No. 3,824,192 of July 16, 1974 and M. Minagawa in U.S. Pat. No. 3,849,370 of Nov. 19, 1974 and in U.S. Pat. No. 3,869,423 of Mar. 4, 1975 are cited as summaries of a very large part of the existing art of phenolic stabilizers. In particular, DiBattista at Column 6 Line 48 to Column 10 Line 49 incudes twelve classes of phenols and over eighty individual members thereof. More recently, J. Song in U.S. Pat. No. 3,795,700 of Mar. 5, 1974 disclosed 4 alkyl-2,6-dimethyl-3-hydroxybenzyl esters of carboxylic acids having the formula: ##STR1## wherein R is branched chain alkyl group containing three to about twelve carbon atoms; Y is the residue of the carboxylic acid Y(COOH).sub.n, provided that when Y is alkyl and n is one, Y contains more than ten carbon atoms; and n is one to four.
1. Hechenbleikner in U.S. Pat. No. 3,839,506 of Oct. 1, 1974 disclosed hindered phenolic phosphonate esters having the formula: ##STR2## where n is an integer of 1 to 4, R is alkyl, hydrogen, cycloalkyl or aralkyl and R' is alkyl, cycloalkyl or aralkyl.
E. Kleiner in U.S. Pat. No. 3,944,594 of Mar. 16, 1976 disclosed hindered phenolic esters having the formula: ##STR3## wherein X is oxygen or sulfur
a is an integer from 2 to 6, PA1 b is an integer from 3 to 40, and PA1 R is ##STR4## wherein R.sub.1 is an alkyl group from 1 to 8 carbon atoms, PA1 R.sub.2 is hydrogen or an alkyl group from 1 to 8 carbon atoms, and PA1 x is an integer from 0 to 6.
Phenolic stabilizers are also employed in conjuction with other stabilizers such as esters of thiodipropionic acid or organic phosphites in the stabilization of polypropylene and other synthetic resins against degradation upon heating or ageing under atmospheric conditions. Disclosures by C. Tholstrup, U.S. Pat. Nos. 3,033,814 of May 8, 1962 and 3,160,680 of Dec. 8, 1964; L. Rayner, U.S. Pat. No. 3,181,971 of May 4, 1965; D. Bown, U.S. Pat. No. 3,242,135 of Mar. 22, 1966; S. Murdock, U.S. Pat. No. 3,245,949 of April 12, 1966; H. Hagemeyer, U.S. Pat. No. 3,282,890 of Nov. 1, 1966; J. Casey, U.S. Pat. Nos. 3,496,128 of Feb. 17, 1970 and 3,586,657 of June 22, 1971; M. Minagawa, U.S. Pat. Nos. 3,549,572 of Dec. 22, 1970, and 3,629,189 of Dec. 21, 1971, and 3,673,152 of June 27, 1972, 3,849,370 of Nov. 19, 1974 and 3,869,423 of Mar. 4, 1975; W. Drake U.S. Pat. No. 3,624,026 of Nov. 30, 1971; A. DiBattista, U.S. Pat. No. 3,824,192 of July 16, 1974; B. Cook, U.S. Pat. No. 3,850,877 and H. Mueller U.S. Pat. No. 3,850,918 of Nov. 26, 1974; M. Dexter U.S. Pat. Nos. 3,856,748 of Dec. 24, 1974, and 3,888,824 of June 10, 1975, and 3,903,160 of Sept. 2, 1975; P. Klemchuk U.S. Pat. No. 3,860,558 of Jan. 14, 1975; M. Rasberger U.S. Pat. Nos. 3,867,340 of Feb. 18, 1975 and 3,901,931 of Aug. 26, 1975; H. Brunetti U.S. Pat. Nos. 3,867,337 of Feb. 18, 1975 and 3,873,498 of Mar. 25, 1975; S. Rosenberger U.S. Pat. No. 3,884,874 of May 20, 1975 and 3,887,518 of June 3, 1975; C. Ramey U.S. Pat. No. 3,907,803 of Sept. 23, 1975 are representative of a very large number of stabilizer combinations including dilauryl and distearyl thiodipropionate or other dialkyl thiodipropionates along with polyhydric phenols and sometimes organic phosphites, metallic stearates, ultraviolet absorbers, nickel compounds, and heavy metal deactivators for use in polypropylene and other polyolefins.
Disclosures by R. Werkheiser, U.S. Pat. No. 2,726,226 of Dec. 6, 1975; I. Salyer et al., U.S. Pat. No. 2,985,617 of May 23, 1961; L. Friedman, U.S. Pat. No. 3,039,993 of June 19, 1962; W. Nudenberg, U.S. Pat. No. 3,080,338 of Mar. 5, 1963; C. Fuchsman, U.S. Pat. No. 3,082,187 of Mar. 19, 1963; H. Orloff et al., U.S. Pat. No. 3,115,465 of Dec. 24, 1963; A. Nicholson, U.S. Pat. No. 3,167,526 of Jan. 26, 1965; A. Hecker et al., U.S. Pat. Nos. 3,149,093 of Sept. 15, 1964, 3,244,650 of Apr. 5, 1966 and 3,225,136 and 3,255,151 of June 7, 1966; C. Bawn, U.S. Pat. No. 3,352,820 of Nov. 14, 1967; D. Miller, U.S. Pat. No. 3,535,277 of Oct. 20, 1970; J. Casey, U.S. Pat. No. 3,586,657 of June 22, 1971; C. Abramoff U.S. Pat. No. 3,856,728 of Dec. 24, 1974; M. Minagawa, U.S. Pat. Nos. 3,869,423 of Mar. 4, 1975 and 3,907,517 of Sept. 23, 1975; and British Pat. Nos. 846,684, 851,670, and 866,883 are representative of stabilizer combinations including organic phosphites, polyhydric phenols, and other active ingredients.
As summarized in a publication by D. Plank and J. Floyd (title--"Polycarbonates: A New Concept in Stabilization for Polypropylene, " meeting preprints, Society of Plastics Engineers, Houston, Texas, April 1975; pages 33-37), there have long been several problems with using pheonols as stabilizers despite their widespread use. Many phenol stabilizers are volatilized out of the polymer at high use temperatures. Some phenol stabilizers are extractable under certain use conditions. The oxidative products of most phenols are highly colored, thus imparting a yellow color to the polymer. Many phenols are reactive towards acidic or basic residues in the polymer. Following are disclosures of suggested ways to overcome these problems.
L. Friedman has disclosed in U.S. Pat. No. 3,053,878 of Sept. 11, 1962 a class of linear phosphite polymers having the formula ##STR5## in which Q is the alkylene or arylene portion of a dihydric alcohol or dihydric phenol. R. Morris et al. in U.S. Pat. No. 3,112,286 of Nov. 26, 1963 disclosed phosphites having the formula ##STR6## in which R represents a bulky hydrocarbon group such as t-butyl, t-amyl, t-hexyl, cyclohexyl, t-pentyl, t-octyl, phenyl, and the like: R.sub.1 represents hydrogen and R; R.sub.3 represents an alkyl group from 6 to 20 carbon atoms which is preferably in the meta or para position; x represents a number of from 1 to 3 inclusive; y represents a number of from 0 to 2 inclusive and the sum of the numerical value of x+y is always exactly 3.
D. Bown, U.S. Pat. No. 3,297,631 of Jan. 10, 1967 disclosed condensation products of phosphorus compounds with bisphenols and trisphenols which may be represented by the structures: ##STR7## Where: X is selected from the following: &gt;P--OR'; &gt;P--R'; ##STR8## and Y is selected from the following:--P(OR').sub.2 ; ##STR9## R is hydrogen, alkyl of 1 to 16 carbon atoms or aryl or a combination of these; R' is alkyl of 1 to 16 carbon atoms or aryl, anf R" is alkylidene of 1 to 16 carbon atoms or an aryl-substituted alkylidene.
C. Baranauckas, U.S. Pat. No. 3,305,608 of Feb. 21, 1967, disclosed phenolic phosphites useful as polymer stabilizers prepared by reacting a triorganophosphite, a polyol, and an aromatic material having two to six phenolic hydroxyl groups at 60.degree.-180.degree. C. in specified proportions.
G. Brindell, U.S. Pat. No. 3,412,064 of Nov. 19, 1968 disclosed phenolic phosphites represented by the general formula: ##STR10## where x is from 1 to 3, y and z each from 0 to 2, x+y+z=3, R is hydrogen or alkyl and Y is hydroxyl or a group of the formula ##STR11## where R is hydrogen or alkyl
M. Larrison, U.S. Pat. No. 3,419,524 of Dec. 31, 1968, disclosed phosphites useful as polymer stabilizers having the formula: ##STR12## where R.sub.1, R.sub.2, R.sub.4, R.sub.6, and R.sub.7 are aryl or haloaryl, and R.sub.3 and R.sub.5 are a polyalkylidene glycol or an alkylidene bisphenol or a hydrogenated alkylidene bisphenol or a ring halogenated alkylidene bisphenol from which the two terminal hydrogens have been removed.
O. Kauder et al., U.S. Pat. Nos. 3,476,699 of Nov. 4, 1969 and 3,655,832 of Apr. 11, 1972 disclosed organic phosphites containing a free phenolic hydroxyl group and defined by the formula: ##STR13## wherein Z is selected from the group consisting of hydrogen and aliphatic, cycloaliphatic, aromatic, heterocyclic and (Ar).sub.p --Y--Ar groups, taken in sufficient number to satisfy the valences of the two phosphite oxygen atoms; Y is a polyvalent linking group selected from the group consisting of oxygen; aliphatic, cycloaliphatic and aromatic hydrocarbon groups attached to each Ar group through a carbon atom not a member of an aromatic ring; oxyaliphatic; thioaliphatic, oxycycloaliphatic, thiocycloaliphatic; heterocyclic; oxyheterocyclic, thioheterocyclic, carbonyl, sulfinyl; and sulfonyl groups; Ar is a phenolic nucleus which can be phenyl or a polycarbocyclic group having condensed or separate phenyl rings; each Ar group is either connected through an oxygen atom to a phosphite group or contains a free phenolic hydroxyl group, or both; and p is a number, one or greater, and preferably from one to four, which defines the number of Ar groups linked to Y.
L. Friedman, U.S. Pat. No. 3,516,963 of June 23, 1970, disclosed phosphites having the formula: ##STR14## where R is alkyl, alkenyl, aryl, aralkyl, haloaryl, haloalkyl or ##STR15## and n is an integer of at least 1. n can be 2, 3, 4, 5, 6, 7, 8, 10, 50, 100 or even more.
D. Bown et al. in U.S. Pat. Nos. 3,510,507 of May 5, 1970 and 3,691,132 of Sept. 12, 1972 disclosed polyolefins stabilized with polyphosphites, polyphosphates, polyphosphonites, polyphosphonates, polyborates, polycarbonates, and polysilanes which are condensation products of a 4,4'-bisphenol with a condensing or linking agent which may be of the ester type, such as the esters of triaryl or mixed aryl-alkyl compounds, or the acid halide type. Bown's condensation product stabilizers have molecular weights between 600 and 8000 or higher and are described by the structural formula, ##STR16## where X is selected from the group consisting of --S--, ##STR17## --C--C, and C--A--C-- where A is a C.sub.1 to C.sub.16 alkylene or an arylene; R', R", R"', and R"" are selected from the group consisting of hydrogen, C.sub.1 to C.sub.18 alkyls, and an aryl group; Y is selected from the group of ##STR18## where R is hydrogen, a C.sub.1 to C.sub.18 alkyl, or aryl; ##STR19## where m is 0 to 10, preferably 4 to 8, ##STR20## where A' is (CH.sub.2).sub.n --S--(CH.sub.2).sub.n or --(CH.sub.2).sub.n --S--(CH.sub.2).sub.m --S--(CH.sub.2).sub.n where n is 0 to 10, preferably 2 and m is 0 to 10, preferably 5; ##STR21## where R is an alkyl, preferably methyl, and Z is ##STR22## where R', R", R"', R"", and X correspond respectively to the R', R", R"', R"", and X previously selected when n has a value from 1 to 15, or Z may be derived from the compound used to introduce Y into the product when n has a value from 2 to 15, for example --R or --OR where R is hydrogen, an alkyl, or aryl. When Y in the formula of Brown's stabilizer is ##STR23## the stabilizer is a type of hydroxyaryl phosphite. Similarly, when Y in the formula is ##STR24## the stabilizer is a hydroxyaryl carbonate.
Bown's condensation products are described as especially effective in high molecular weight solid polyolefins when used together with a dialkyl sulfide costabilizer such as dilauryl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, dicetyl sulfide, bis(tetradecylmercapto) paraxylylene, and 10,24-dithiotetracontane.